Cyclodextrins (CD) are macromolecules which are known for their ability to form inclusion complexes with a wide variety of molecules. A recent area of interest in the field of CD research is the coating of solid materials with CD in order to achieve a functional solid material surface.
The fixation of CD onto a solid material can be achieved in a number of ways. A fixation can range from weak van der Wall interactions to covalent grafting on the solid material. Covalent grafting has attracted considerable attention, whereas the non-covalently grafting has attracted much less attention.
A paper by Cristiano et al. (Langmuir 2007, 23, 8944-8949) discloses a method for the adsorption and spreading of β-cyclodextrin (β-CD) vesicles on hydrophobic and hydrophilic solid material surfaces, which involves a transition from bi-layer vesicles to planar molecular mono-layers or bi-layers. The CD vesicles prefer to interact with hydrophobic and cationic solid material surfaces instead of hydrophilic, non-ionic solid material surfaces. The adsorption of CD vesicles on hydrophobic solid material surfaces results in solid-supported mono-layers of CD in which the alkyl chains of the CD layer cover the hydrophobic solid material surface and leave the hydrophilic part exposed to the aqueous solution. The adsorption of CD vesicles on cationic solid material surfaces results in solid-supported bi-layers of CD. Also in this case, the hydrophilic face of the CD is exposed to the solution. The supported layers function as a supra-molecular platform that can bind suitable guest molecules through inclusion in the CD host cavities. However, the limitation to mono- and bi-layers of this method makes it unsuitable for e.g. the textile industry, which needs a thicker CD-layer to obtain a high load of guest molecules.
WO 02/077000 discloses macrocyclic oligosaccharide derivatives, such as cyclodextrines, wherein the subunits making up the macrocycle are modified to enable the macrocycle to self assemble in a suitable solvent to form elongated assemblies comprising a plurality of macrocyclic units. These elongated assemblies have the ability to encapsulate guest molecules such as therapeutic drugs and can be used as hosts for the solubilisation of various compounds. However, a method for grafting the macrocyclic oligosaccharide derivatives onto solid material surfaces is not disclosed.
Several methods for the modification of surfaces with cyclodextrins have been presented in previous art, but only a few aims at creating multiple layers of cyclodextrin with subsequently larger capacity compared to a mono-layer. Multiple layers can be achieved by physical entrapment of cyclodextrins in a polymer matrix covering the surface, as disclosed in WO2009/033635, or by forming a physically immobilized polymer around a e.g. fabric fiber from cyclodextrins by use of either reactive cyclodextrin derivatives (JP2009013547) or by use of chemical cross-linking. Both approaches require time consuming processing and the use of chemical reactants and are as such not suitable for large scale production or coating of surfaces.
Hence, a method for non-covalent grafting onto solid material surfaces would be advantageous.